ctl_ioctl_frontend: Reject out-of-range initiator IDs

Various places in CTL assume that initiator IDs are not larger than
CTL_MAX_INIT_PER_PORT. Other IDs such as lun IDs are validated in
places such as ctl_scsiio_precheck, but initiator IDs submitted by
userland were not previously validated.

PR: 291059
Reported by: Hans Rosenfeld <rosenfeld@grumpf.hope-2000.org>
Reviewed by: asomers
Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D56628